Automated longitudinal position translator for ultrasonic imaging probes, and methods of using same

ABSTRACT

A longitudinal position translator includes a probe drive module and a linear translation module. The probe drive module is coupled operatively to an ultrasonic imaging probe assembly having a distally located ultrasound transducer subassembly in such a manner that longitudinal shifting of the transducer subassembly may be effected. The probe drive module is preferably mounted to the linear translation unit so as to be moveable between a condition whereby longitudinal shifting of the transducer subassembly can be conducted either manually or automatically. When in the automatically-operable condition, the probe drive module will be engaged with a motor-driven screw associated with the linear translation module so as to cause the probe drive module to be longitudinally displaced at a constant motor-driven rate. In this manner, the distally located ultrasound transducer is longitudinally shifted during an ultrasound scan of surrounding intravascular (or other) tissue to thereby allow axially-spaced 360° data sample &#34;slices&#34; of the surrounding tissue to be obtained. The data samples may then be reconstructed into a three-dimensional or other two-dimensional representations of the scanned vessel to assist in diagnosis.

CROSS-REFERENCE TO RELATED PATENTS AND APPLICATIONS

This application is related to commonly owned U.S. Pat. No. 5,115,814issuing on May 26, 1992 to James M. Griffith et al, and entitled"Intravascular Ultrasonic Imaging Probe and Methods of Using Same",which is the parent of commonly owned and copending U.S. patentapplication Ser. No. 07/840,134 filed on Feb. 24, 1992, the entirecontent of each being expressly incorporated hereinto by reference.

FIELD OF INVENTION

The present invention generally relates to elongate probe assemblies ofsufficiently miniaturized dimensions so as to be capable of navigatingtortuous paths within a patient's organs and/or vessels. In preferredforms, the present invention is embodied in automated units which areconnectable to a probe assembly having a distally located ultrasoundtransducer subassembly which enables the transducer subassembly to bepositioned accurately by an attending physician and then translatedlongitudinally (relative to the axis of the elongate probe assembly)within the patient under automated control.

BACKGROUND OF THE INVENTION

I. Introductory Background Information

Probe assemblies having therapeutic and/or diagnostic capabilities arebeing increasingly utilized by the medical community as an aid totreatment and/or diagnosis of intravascular and other organ ailments. Inthis regard, U.S. Pat. No. 5,115,814 discloses an intravascular probeassembly with a distally located ultrasonic imaging probe element whichis positionable relative to intravascular sites. Operation of theultrasonic element in conjunction with associated electronic componentsgenerates visible images that aid an attending physician in his or hertreatment of a patient's vascular ailments. Thus, a physician may viewin real (or essentially near real) time intravascular images generatedby the ultrasonic imaging probe element to locate and identifyintravascular abnormalities that may be present and thereby prescribethe appropriate treatment and/or therapy.

The need to position accurately a distally located operative probeelement relative to an intravascular site using any therapeutic and/ordiagnostic probe assembly is important so that the attending physiciancan confidently determine the location of any abnormalities within thepatient's intravascular system. Accurate intravascular positioninformation for the probe assembly will also enable the physician tolater replicate probe positions that may be needed for subsequenttherapeutic and/or diagnostic procedures. For example, to enable thephysician to administer a prescribed treatment regimen over time and/orto later monitor the effects of earlier therapeutic procedures.

Recently ultrasonic imaging using computer-assisted reconstructionalgorithms has enabled physicians to view a representation of thepatient's interior intravascular structures in two or three dimensions(i.e., so-called three dimensional or longitudinal view reconstruction).In this connection, the current image reconstruction algorithms employdata-averaging techniques which assume that the intravascular structurebetween an adjacent pair of data samples will simply be an average ofeach such data sample. Thus, the algorithms use graphical "fill in"techniques to depict a selected section of a patient's vascular systemunder investigation. Of course, if data samples are not sufficientlyclosely spaced, then lesions and/or other vessel abnormalities may infact remain undetected (i.e., since they might lie between a pair ofdata samples and thereby be "masked" by the image reconstructionalgorithms mentioned previously).

In practice, it is quite difficult for conventional ultrasonic imagingprobes to obtain sufficiently closely spaced data samples of a sectionof a patient's vascular system under investigation since thereconstruction algorithms currently available depend upon the software'sability to process precisely longitudinally separated data samples. Inthis regard, conventional intravascular imaging systems depend uponmanual longitudinal translation of the distally located ultrasoundimaging probe element by an attending physician. Even with the mostskilled physician, it is practically impossible manually to exerciseconstant rate longitudinal translation of the ultrasound imaging probe(which thereby provides for a precisely known separation distancebetween adjacent data samples). In addition, with manual translation,the physician must manipulate the translation device while observing theconventional two dimensional sectional images. This division of thephysician's attention and difficulty in providing a sufficiently slowconstant translation rate can result in some diagnostic informationbeing missed. In order to minimize the risk that diagnostic informationis missed, then it is necessary to devote more time to conducting theactual imaging scan which may be stressful to the patient.

Thus, what has been needed in this art, is an ultrasound imaging probeassembly which is capable of being translated longitudinally within asection of a patient's vascular system at a precise constant rate. Suchan ability would enable a series of corresponding precisely separateddata samples to be obtained thereby minimizing (if not eliminating)distorted and/or inaccurate reconstructions of the ultrasonicallyscanned vessel section (i.e., since a greater number of more closelyspaced data samples could reliably be obtained). Also, such an assemblycould be operated in a "hands-off" manner which would then allow thephysician to devote his attention entirely to the real time images withthe assurance that all sections of the vessel were displayed. In termsof reconstruction, the ultrasound imaging probe could be removedimmediately and the physician could interrogate the images or theiralternative reconstructions on a near real time basis. Such a feature isespecially important during coronary diagnostic imaging since minimaltime would be needed to obtain reliable imaging while the blood flowthrough the vessels is blocked by the probe assembly. It is thereforetowards fulfilling such needs that the present invention is directed.

II. Information Disclosure Statement

One prior proposal for effecting longitudinal movements of a distallylocated operative element associated with an elongate probe assembly isdisclosed in U.S. Pat. No. 4,771,774 issued to John B. Simpson et al onSep. 20, 1988 (hereinafter "Simpson et al '774"). The device disclosedin Simpson et al '774 includes a self-contained motor drive unit forrotating a distally located cutter element via a flexible drive cablewith manual means to effect relative longitudinal movements of therotating cutter element.

More specifically, in Simpson et al '774, the proximal end of a flexibledrive cable is slidably coupled to a hollow extension rotary drive shaftwith a splined shaft. The hollow extension drive shaft is, in turn,coupled to a motor, whereas the splined shaft cooperates with a manuallyoperated slide member. Sliding movements of the slide member relative tothe motor drive unit housing translate into direct longitudinalmovements of the flexible drive cable, and hence the distally locatedcutter element. In brief, this arrangement does not appear to allow forautomated longitudinal movements of the distally located probe element.

SUMMARY OF THE INVENTION

The longitudinal position translator of the present invention isespecially adapted for use with an intravascular probe assembly of typedisclosed in the above-mentioned U.S. Pat. No. 5,115,814 (incorporatedfully by reference hereinto). That is, the preferred intravascular probeassembly with which the position translator of the present invention maybe used will include a flexible guide sheath introduced along a tortuouspath of a patient's vascular system, and a rotatable probe element(preferably an ultrasonic imaging probe) which is operatively introducedinto the lumen of the guide sheath. Of course, the position translatorof the present invention may be modified easily to accomodate lesscomplex one-piece ultrasonic probe assemblies. Rotational movementssupplied by a patient-external motor are transferred to a distallylocated transducer subassembly by means of a flexible torque cable whichextends through the guide sheath.

As is described more completely in U.S. Pat. No. 5,115,814, the interiorof the guide sheath provides a bearing surface against which the probeelement rotates. This bearing surface supports the probe element duringits rotation so that virtually no "play" is present--that is, so thatthe probe element rotates essentially coaxially relative to the vascularvessel undergoing therapy and/or investigation. The probe element isalso longitudinally (i.e. axially) movable so that axial-spaced 360°data sample "slices" of the patient's vascular vessel wall can beimaged.

The automated longitudinal position translator of the present inventiongenerally includes a probe drive module and a linear translation module.The probe drive module is most preferably embodied in an elongatebarrel-shaped housing structure having a manual positioning levercapable of reciprocal movements between advanced and retractedpositions. The lever captures a proximal end of the guide sheath withinwhich a probe element is disposed. A flexible torque cable connects thetransducer subassembly at the distal end of the probe element to a driveshaft which is driven, in the preferred embodiment, by a precisionrate-controlled motor located in a separate fixed base unit. Preferably,the housing is hinged in a "clamshell" fashion to more easily facilitateelectrical and mechanical coupling of the intravascular probe assembly.The lever may be eliminated when using less complex one-piece ultrasonicprobe assemblies or modified so as to capture the guide catheter orintroducer.

The linear translation module supports the probe drive module. Inaddition, the linear translation module is coupled operatively to theprobe drive module so as to allow for relative hinged movements therebyand thus permit the probe drive module to be moved between amanually-operable condition (whereby the probe drive module isdisengaged from the longitudinal drive subassembly associated with thelinear translation module to thereby allow a physician to exercisemanual control over the longitudinal positioning of the probe element)and an automated condition (whereby the probe drive module isoperatively engaged with the linear translation module so that automatedlongitudinal position control over the probe element can be exercised).

In use, the ultrasound imaging probe will be physically positioned by anattending physician within a section of a patient's vascular systemunder investigation using conventional fluoroscopic positioningtechniques. Thereafter, the proximal portion of the probe and guidesheath assembly will be coupled to the probe drive module. The probedrive module can then be employed to either manually or automaticallytranslate the imaging probe element longitudinally within the section ofthe patient's vascular system under investigation during an ultrasonicimaging scan of the same as may be desired by the attending physician bymoving the probe drive module between its manual and automatedconditions, respectively. The present invention thus allows the distallylocated probe element to be rotated, while simultaneously providing theattending physician with the capability of longitudinally translatingthe probe element at a constant automated translation rate to therebyobtain reliable data samples representative of longitudinallyspaced-apart data "slices" of the patient's vascular section underinvestigation. These data "slices" may then be reconstructed usingconventional computer-assisted algorithms to present the entire sectionof the patient's vascular system under investigation in a moreinformative "two-dimensional" longitudinal or "three-dimensional" imagedisplay on a CRT (or other) monitor. The physician can thus manipulatethe image orientation or two-dimensional sectional plane of the vascularsection electronically and thereby achieve a more informativerepresentation of the condition of the patient's vascular section underinvestigation.

In its preferred embodiment, the linear position translator provides forautomated translation of the imaging probe from a distal location to aproximal location only. Thus, the imaging probe would not be advancedunder automated control into the guide sheath. Such a preferredfunctional attribute eliminates the need for sophisticated sensor andcontrol systems to sense and stop probe advancement should it encountera "kink" or non-negotiable sharp bend in the guiding sheath.Furthermore, during probe withdrawal (i.e., distal to proximal motion),the guide sheath is supported by the probe and may not "kink". Also,since the probe has already negotiated all bends during its initialmanual distal advancement, the attending physician is assured that thebends are in fact negotiable by the probe upon its withdrawal throughthat same path. Thus, although the preferred embodiment contemplatesautomated longitudinal translation in a proximal direction, it islikewise preferred that the attending physician advance the probe in adistal direction manually so that the physician may use his or herexperience with the catheters and the tactile sensations to judge whenan obstruction has been encountered.

Further features and advantages of the present invention will becomemore clear after careful consideration is given to the followingdetailed description of presently preferred exemplary embodiments.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Reference will hereinafter be made to the accompanying drawings whereinlike reference numerals throughout the various FIGURES denote likestructural elements, and wherein;

FIG. 1 is a schematic view of an ultrasonic imaging system that includesan automated longitudinal position translator according to the presentinvention;

FIG. 2 is a top plan view of the probe drive module employed with thelongitudinal position translator according to the present inventionshowing the housing thereof in an opened state;

FIG. 3 is a side elevation view, partly in section, of the probe drivemodule shown in FIG. 2;

FIGS. 4A and 4B are each side elevation views of the longitudinalposition translator according to the present invention in its automatedand manual conditions, respectively;

FIGS. 5A and 5B are each top plan views of the longitudinal positiontranslator according to the present invention in its automated andmanual conditions, respectively;

FIGS. 6A and 6B are each front end elevational views of the longitudinalposition translator according to the present invention in its automatedand manual conditions, respectively;

FIG. 7 is a partial side elevational view which is also partly insection of the longitudinal position translator according to the presentinvention; and

FIGS. 8A-8C are top plan views of the longitudinal position translatoraccording to this invention which schematically depict a preferred modeof automated operation.

DETAILED DESCRIPTION OF THE PREFERRED EXEMPLARY EMBODIMENTS

A schematic diagram of an exemplary ultrasound imaging system 10 isshown in accompanying FIG. 1. System 10 generally includes an ultrasoundimaging probe assembly 12 having a guide sheath 14 and a distallylocated ultrasound imaging probe element 16 inserted into the lumen ofguide sheath 14, the probe element 16 being depicted in FIG. 1 as beingvisible through the guide sheath's transparent wall. The ultrasonicimaging probe assembly 12 preferably embodies those features more fullydescribed in the above-identified U.S. Pat. No. 5,115,814.

The overall length of the imaging probe assembly 12 is suitable for thedesired diagnostic and/or therapeutic intravascular procedure. Forexample, the overall length of the probe assembly 12 may be shorter fordirect (e.g., arteriotomy) insertions as compared to the length of theprobe assembly 12 needed for percutaneous distal insertions (e.g., viathe femoral artery). A representative length of the imaging probeassembly 12 is therefore shown in the accompanying drawings for clarityof presentation.

The terminal end of the guide sheath 14 preferably carries a radiopaquemarker band 18 formed of gold or other fluoroscopically visiblematerial. The marker band 18 allows the attending physician to monitorthe progress and position of the guide sheath 14 during intravascularinsertions using standard fluoroscopic imaging techniques.

The proximal end of the imaging probe assembly 12 is received within aprobe drive module 20. In essence, the probe drive module 20 includes adistally open-ended and longitudinally barrel-shaped housing 22, and apositioning lever 24 which captures the proximal end of the guide sheath14. The proximal end of the ultrasound imaging probe element 16 ismechanically and electrically connected to the probe drive module 20.Longitudinal reciprocal movements of the positioning lever 24 relativeto the housing 22 will thus in turn effect relative longitudinaldisplacements of the distal end of the probe element 16 within the guidesheath 14 relative to the longitudinal axis of the probe assembly 12.

The probe drive module 20 also includes a drive unit 26 fixedlyconnected proximal to the housing 22 and contains the structures whichsupply mechanical rotation and electrical signals to the probe element16. In the preferred embodiment, mechanical rotation of the probeelement 16 is provided by a separate precision motor 28 associated witha base unit (not shown) and operatively coupled to the probe drivemodule 20 via a flexible drive cable 28a. It is entirely conceivable,however, that the drive unit 26 could be sized so as to accomodate themotor 28.

The drive unit 26 is most preferably configured so that the attendingphysician may comfortable grasp its exterior with one hand while theprobe drive module 20 is in its manual condition. The drive unit 26 thusforms a handle which allows the physician to manually manipulate therelative position between the housing 22 and the positioning lever 24thereby responsively permitting manual longitudinal movements to beimparted to the probe element 16. A thumb/finger switch 30 may thus bemanually depressed to allow the physician to selectively operate thedrive unit 26 and thereby rotate the ultrasonic imaging probe element 16when it is desired to conduct an ultrasonic imaging scan. Electricalconnection between the switch 30 and the control console 46 is made viaI/O cabling 41.

During rotation, electrical communication is established between thetransducer subassembly in the distal end of the ultrasonic imaging probeelement 16 and the ultrasound transceiver 40 via patient-internalelectrical coaxial cabling (not shown) within the probe element 16,drive unit 26 and electrical patient-external I/O cabling 41. Theultrasound transceiver 40 produces a pulse signal (of desired magnitudeand shape) which is applied via the electrical cabling 41 to anelectroacoustic transducer associated with the distal end of the probeelement 16. The transceiver 40 also performs conventional signalprocessing operations (e.g., amplification, noise reduction and thelike) on electrical signals generated by the electro-mechanicalexcitation of the transducer within the probe element 16 (i.e., signalsgenerated by the transducer in response to receiving acoustic echowaves).

These signals are further processed digitally via known displayalgorithms (e.g., conventional PPI (radar) algorithms) and are thensupplied as input to a CRT monitor 42 (or any other equivalent displaydevice) so as to generate an ultrasound image 44 of desired formatrepresentative of the vascular structures reflecting ultrasonic energytoward the transducer within the distal end of the probe element 16. Acontrol console 46 may be employed by the attending physician so as toselect the desired operational parameters of the ultrasound transceiver40 and/or the display format of the image 44 on the CRT 42, for example.

The probe drive module 20 is operatively coupled to and supported by thelinear translation module 48 so as to allow for reciprocal rectilinearmovements of the housing 22/drive unit 26 relative to both the lineartranslation module 48 and the positioning arm 24 which collectivelyremain in a fixed position as will be described in greater detail below.As will also be described in greater detail below, the probe drivemodule 20 is mounted for hinged movements relative to the lineartranslation module 48 between a manually-operable condition (whereby theprobe drive module 20 is operatively disengaged from the motor driventranslator associated with the linear translation module 48) and aautomatically-operable condition (whereby the probe drive module 20 isoperatively engaged with the motor driven translator associated with thelinear translation module 48).

The linear translation module 48 includes a proximal housing 48a whichcontains appropriate speed-reducers, drive shafts and associatedcouplings to be described below in connection with FIG. 7. Suffice it tosay here, however, that driven power is provided to the structuresinternally of housing 48a by a separated precision motor 50 associatedwith a system base unit (not shown) which is coupled operatively to thestructures internally of housing 48a via a flexible drive shaft 50a.Again, it is entirely conceivable that the housing 48a of the lineartranslation module 48 could be sized and configured so as to accomodatethe motor 50. Automated operation of the motor 50 (and hence the lineartranslation module 48) may be accomplished through the selection ofappropriate operation parameters by the attending physician via controlconsole 46. Operation of both the linear translation module 48 and theprobe drive module 20 may be initiated by depressing the foot-switch 27.

The exemplary probe drive module 20 which is employed in the presentinvention is perhaps more clearly depicted in accompanying FIGS. 2 and3. As is seen, the housing 22 is collectively formed of a pair ofelongate lower and upper housing sections 51, 52, respectively, whichare coupled to one another along adjacent longitudinal edges in aclamshell-hinged arrangement via hinge pin 54.

It will be noticed with particular reference to FIG. 2 that the proximaland distal ends 54a, 54b of pin 54 are rigidly fixed to the proximal anddistal ends 51a, 51b of housing section 51, respectively, while thehousing section 52 is pivotally coupled to the pin 54 (and hence thehousing section 51) by means of proximal and distal and intermediatepivot sleeves 56a, 56b and 56c, respectively. The housing sections 51,52 are maintained in their closed state (i.e., as shown in FIGS. 4Athrough 5B) by means of a spring-loaded detent 57a (see FIG. 2) whichmay be moved into and out of an aperture (not shown) formed in thehousing section 51 via operating lever 57b.

The positioning lever 24 is oriented transversely relative to theelongate axis of housing 22. In this regard, the lever 24 includes asleeve end 24a which is coupled to the pivot pin 54 to allow reciprocallongitudinal and pivotal movements of the lever 24 to occur relative tothe longitudinal axis of pin 54. The opposite end 24b of lever 24extends radially outwardly from the housing 22.

The housing 22 defines an elongate slot 58 when the housing sections 51,52 are in a closed state (i.e., as depicted in FIG. 1). The slot 58allows the positioning lever 24 to be manually moved along thelongitudinal axis of pin 54 during use (i.e., when the housing sections51, 52 are in a closed state) between retracted and extended positions(shown respectively by phantom line representations 24' and 24" in FIG.2). The retracted position 24' of lever 24 is established by a distalface of a pivot sleeve 56c integral with the housing section 52 andpivotally coupled to pin 54 in a manner similar to pivot sleeves 56a and56b. On the other hand, the extended position 24" of lever 24 isestablished by a proximal face of pivot sleeve 56b.

The lever 24 is supported by a concave inner surface 59 formed in thehousing section 51 when the housing sections 51 and 52 are in a closedstate. The inner surface 59 provides a bearing surface against which thelever 24 slides during the latter's movement between its retracted andextended positions 24' and 24", respectively.

A scale 60 (see FIGS. 4A and 5A) preferably is provided on the housing22. A pointer 24c associated with the lever 24 may be aligned with thescale 60 to provide an attending physician with information regardingthe position of probe element 16 relative to its most distal positionwithin the guide sheath 14. That is, longitudinal movement of lever 24an incremental distance (as measured by pointer 24c and the scale 60)will effect movement of the probe element 16 relative to its most distalposition within the guide sheath's distal end by that same incrementaldimension.

Accompanying FIG. 2 also more clearly shows the cooperative engagementbetween positioning lever 24 and the proximal end of guide sheath 14. Inthis regard, it will be noted that the proximal end of guide sheath 14includes a side-arm port 70 which extends generally transverse to thelongitudinal axis of guide sheath 14. Side-arm port 70 includes aconventional Leur-type locking cap 72 that is coupled coaxially to asimilar locking cap 74 associated with the proximal end of guide sheath14. Side-arm port 70 is thus in fluid-communication with the lumen ofguide sheath 14 so that saline solution, for example, may be introducedvia side-arm tubing 70a.

A shaft extension 75 of probe element 16 and electrical cablingcoaxially carried thereby are mechanically and electrically coupled tothe output shaft 77 of the probe drive module 20 via coaxial cablecouplings 75a and 75b. It will be appreciated that coaxial cablingwithin the flexible torque cable portion of probe element 16 (not shown)will rotate with it as a unit during operation, but that the electricalI/O signals will be transferred to transceiver 40 by means of couplings75a and 75b. The manner in which the separate electrical I/O path(represented by cable 41--see FIG. 1) and mechanical input path(represented by the flexible drive shaft 28a--see FIG. 1) are combinedinto a common electrical/mechanical output path (represented by outputshaft 77) will be explained in greater detail with reference to FIG. 3.

The shaft extension 75 is preferably fabricated from a length ofconventional stainless steel hypodermic tube and is rigidly coupled atits distal end to a flexible torque cable (not shown). As mentionedbriefly above, the torque cable extends the length of the guide sheath14 and is connected at its distal end to a transducer subassembly in thedistal end of the probe element 16. The torque cable thereby transfersthe rotational motion imparted via the motor to shaft extension 75 ofthe probe element 16 causing the transducer subassembly to similarlyrotate within the lumen of the guide sheath 14 near the guide sheath'sdistal end, as well as to be longitudinally shifted within guide sheath14 via manipulation of the relative position of the arm 24.

The shaft extension 75 extends through an end cap 76 which is coupledcoaxially to locking caps 72 and 74. End cap 76 houses a synthetic resinbearing element (not shown) which serves as a proximal rotationalbearing for the shaft 75, and also serves to seal the proximal end ofguide sheath 14 against fluid (e.g., saline liquid) leakage.

Lever 24 defines a pair of mutually transverse concave cradle surfaces80 and 82. The longitudinal dimension of cradle surface 80 is orientedparallel to the longitudinal dimension of housing 22, whereas cradlesurface 82 (which is joined at one of its ends to the cradle surface 80)is oriented transverse to the longitudinal dimension of housing 22(i.e., since it is traverse to cradle surface 80).

Cradle surface 80 is sized and configured so as to accomodate anexterior surface portion of coaxially locked caps 72, 74 and 76. Cradlesurface 82, on the other hand, is sized and configured to acceptside-arm port 70 and side-arm tubing 70a extending therefrom. An axiallyextending inner concave surface 84 is defined in housing section 52 and,like cradle surface 82, is sized and configured so as to accept anexterior portion of locking caps 72, 74 and 76.

When housing sections 51 and 52 are in a closed state, caps 72, 74 and76 will be enveloped by housing 22. More specifically, inner concavesurface 84 will positionally restrain caps 72, 74 and 76 within cradlesurface 80 when housing sections 51 and 52 are closed. Since side-armport 70 will likewise be positionally restrained within cradle surface82 when housing sections 51, 52 are closed, caps 72, 74 and 76 will bemoved longitudinally as a unit with position lever 24. That is,longitudinal movements of lever arm 24 between its retracted andextended positions will cause the proximal end of guide sheath 14 (i.e.,coaxially mounted caps 72, 74 and 76) to be longitudinally movedrelative to the longitudinally stationary (but axially rotatable) shaftextension 75. In such a manner, the proximal end of guide sheath 14 willbe moved closer to and farther from the open distal end of housing 22.

As can be seen in FIG. 3, the interior of the drive unit 26 is hollow tohouse electrical/mechanical coupling assembly 85. Electrical/mechanicalcoupling 85 combines an electrical input path--represented by coaxialI/O cable 41 which establishes electrical communication with transceiver40--and a mechanical input path--represented by flexible drive shaft 28aassociated with motor 28 (see FIG. 1) into a common coaxial output shaft77.

Output shaft 77 is rotatably held within bearing block 86 and includes arearwardly extending rotatable tail portion carrying a number ofelectrical slip-rings 86a. Electrical communication between theslip-rings 86a and coupling 75b is established by a length of coaxialcable (not shown) housed within the output shaft 77. Stationary brushes88a in sliding electrical contact with respective ones of the slip-rings86a are associated with a brush block 88. Lead wires 88b are, in turn,coupled electrically at one end to brush block 88 (and hence to coaxialconnector 75a via brushes 88a and slip-rings 86a), and at the other endto coaxial I/O cable 41 via a ferrite coil transformer (not shown).Slip-rings 86a, brushes 88a, brush block 88, lead wires 88b, and ferritecore transformer (not shown) are housed within a common electricallyshielded enclosure 90.

The mechanical input path generally represented by flexible drive shaft28a is coupled operatively to one end of a rigid rotatable drive shaft92 carrying a drive gear 94 at its other end. Drive gear 94 is, in turn,meshed with a gear 96 carried by output shaft 77. Upon rotation of driveshaft 92, meshed gears 94, 96 will cause shaft 77 to responsivelyrotate. Preferably, gears 94 and 96 are in a 1:1 ratio, but other gearsizes (and hence ratios) may be provided if desired.

The probe drive unit 20 is mounted for reciprocal rectilinear movementsto the linear translation module 48 as is shown in accompanying FIGS. 4Athrough 6B. In this regard, the linear translation module includes abase plate 100 which supports the housing 48a and its internalstructures (to be described below with reference to FIG. 7). The probedrive module 20 itself includes a longitudinally spaced-apart pair ofsupport flanges 102, 104, each of which is slidably mounted onto a pairof parallel guide rails 106, 108.

The proximal end of guide rail 106 is pivotally connected to the housing48a while its distal terminal end is pivotally connected to an uprightsupport block 106a. A forward and rearward pair of transverse supportarms 110, 112 each having one end rigidly coupled to guide rail 106 andan opposite end rigidly coupled to the guide rail 108. Thus, the supportarms 110, 112 are capable of pivoting between a lowered position (e.g.,as shown in FIGS. 4A, 5A and 6A) and a raised position (e.g., as shownin FIGS. 4B, 5B and 6B) by virtue of the pivotal guide rail 106 so asto, in turn, pivotally move the probe drive module 20 between itsautomatically-operable condition and its manually-operable condition,respectively, due to its attachment to the guide rails 106, 108 viasupport flanges 102, 104.

The ends of each transverse support arm 110, 112 between which the guiderail 108 is fixed are removably captured by upright restraining posts114, 116, respectively. As is perhaps more clearly shown in FIGS. 6A and6B, the restraining posts 114, 116 (only restraining post 114 beingvisible in FIGS. 6A and 6B) are rigidly supported by the base plate 100and include an inwardly projecting lip 114a, 116a which provide aninterference fit with the terminal ends of support arms 110, 112,respectively. In this connection, it is preferred that the restrainingposts 114, 116 be formed of a relatively stiff, but resilient plasticsmaterial (e.g., nylon, polyacetal or the like) so that when the probedrive unit is moved between its automatically-operable andmanually-operable conditions, the posts 114, 116 are capable of yieldingsomewhat to allow such movement.

The positioning arm 24 of the probe drive unit 20 is fixedly tied to theforward transverse support arm 110 by an upright connector 120a on alongitudinal connector 120b. In this regard, the upper end of uprightconnector 120a extends through a longitudinal slot on the side of thehousing 22 opposite slot 58 and positionally captures the ends of thepositioning arm 24 around pin 54. The lower end of the upright connector120a is connected to the distal end of the horizontally disposedlongitudinal connector 120b. The proximal end longitudinal connector120b is, in turn, rigidly fixed to the transverse support arm 110 by anysuitable means (e.g., screws). It will be understood, therefore, thatthe position of the positioning arm 24 (and hence the guide sheath 14)remains fixed relative to the base 100 of the linear translation module48 during longitudinal movements of the probe drive module 20 along theguide rails 106 and 108. Thus, the relative position of thepatient-internal transducer subassembly at the distal end of the probeelement 16 will correspondingly shift the same distance as the probedrive module 20 relative to the patient internal distal end of the guidesheath 14.

Automated longitudinal shifting of the probe drive module 20 (and hencethe ultrasonic transducer subassembly at the distal end of the probeelement 16) is permitted by the coaction between a longitudinallyextending drive screw 120 and a threaded collar portion 122 (see FIGS.4B and 7) associated with the support flange 102 of the probe drivemodule 20. The distal and proximal ends of the drive screw 120 arerotatably supported by an upright distal bearing block 124 and anupright proximal bearing block 126 (see FIG. 7), respectively.

As can be seen in FIGS. 4B, 5B, 6B and 7, the threaded collar portion122 is disengaged from the threads of drive screw 120 when the probedrive module 20 is in its manually-operable condition. As a result, theattending physician may simply manually shift the probe drive module 20longitudinally along the guide rails 106, 108. When the probe drivemodule 20 is pivoted into its automatically-operable condition as shownin FIGS. 4A, 5A and 6A, the threads associated with the threaded collarportion 122 will be mateably engaged with the threads of the drive screw120. As a result, rotation of the drive screw 120 about its longitudinalaxis will translate into longitudinal displacement of the probe drivemodule 20. The threads of the drive screw 120 and the threaded collarportion 122 as well as the rotation direction of the drive screw 120 aremost preferably selected so as to effect longitudinal shifting of theprobe drive module from the distal end of the drive screw towards theproximal end thereof--i.e., a distal to proximal displacement. However,these parameters could be changed so as to effect a reverse (proximal todistal) displacement of the probe drive unit, if necessary or desired.

The drive screw 120 is coupled operatively to the flexible drive shaft50a (and hence to the driven output of motor 50) by the structurescontained within housing 48a. In this regard, the proximal end of thedrive screw is coupled to the output shaft of a speed reducer 128 via ashaft coupling 130. The input to the speed reducer 128 is, in turn,coupled to the flexible drive shaft 50a from a rigid shaft extensionmember 132 and its associated shaft couplings 132a and 132b. The speedreducer 128 is of a conventional variety which provides a predeterminedreduced rotational speed output based on the rotational speed input.Preferably, the motor 50, speed reducer 128 and drive screw 120 aredesigned so as to effect longitudinal translation of the probe driveunit 20 at a rate of between about 0.25 to 1.0 mm/sec. Of course, otherlongitudinal translation rates may be provided by varying the parametersof the motor 50, speed reducer 128 and/or drive screw 120.

In use, the attending physician will preposition the guide sheath 14 andimaging probe element 16 associated with the ultrasound imaging probeassembly 12 within the vessel of the patient to be examined usingstandard fluoroscopic techniques and/or the techniques disclosed in theabove-mentioned U.S. Pat. No. 5,115,814. Once the guide sheath14/imaging probe element 16 have been prepositioned in a region of thepatient's vessel which the physician desires to observe, the proximalend of the probe assembly 12 will be coupled to the probe drive module20 in the manner described above. Thereafter, the physician may conductan ultrasound scan of the patient's vessel by operating switch 30 tocause high-speed rotation of the transducer subassembly on the distalend of the probe element 16 within the guide sheath 14. Data samplesassociated with different transverse sections of patient's vessel maythen be obtained by the physician manually shifting the probe drivemodule 20 along the guide rails 106, 108 in the manner described above.

Alternatively, the physician may elect to pivot the probe drive module20 into its automatically-operable condition and then select automatedoperation of the same via the control console 46 and foot-switch 27. Insuch a situation, the probe drive module (and hence the transducersubassembly at the distal end of the probe element 16) will be shiftedlongitudinally at a constant rate simultaneously with high-speedrotation of the transducer subassembly. In this manner, data samplesrepresenting longitudinally spaced-apart 360° "slices" of the patient'sinterior vessel walls will be accumulated which can then bereconstructed using known algorithms and displayed in "two-dimensional"or "three-dimensional" formats on the monitor 42.

Accompanying FIGS. 8A-8C schematically depict the longitudinaltranslator according to this invention being operated in an automatedmanner. In this connection, and as was noted briefly above, the probedrive module 20 is most preferably translated in a distal to proximaldirection by means of the linear translation module 48 (i.e., in thedirection of arrows 140 in FIGS. 8A and 8B). In FIG. 8A, the probe drivemodule is shown in a position at the beginning of an automatedultrasonic imaging scan, it being noted that the pointer 24c associatedwith the positioning arm 24 registers with the zero marking on the scale60. The physician will then initiate automated ultrasonic scanning viathe foot-switch 27 which causes the probe drive unit 20 to be displacedproximally (arrow 140) at a constant rate as shown in FIG. 8B. Thisproximal displacement of the probe drive module 20 will, in turn, causethe transducer subassembly on the distal end of the probe element 16 tobe longitudinally displaced proximally (i.e., pulled back away from) thedistal-most end of the guide sheath 14.

The ultrasonic imaging scan is automatically terminated (e.g., by use ofsuitable limit switches and/or position transducers) when the probedrive unit reaches the its most proximal position as shown in FIG. 8C.In this connection, the present invention most preferably is providedwith a limit switch (not shown) enclosed within a limit switch housing29 (see FIGS. 4a and 5B) which is mechanically actuated when supportflange 102 contacts support arm 112 (i.e., when the probe drive module20 is in its most proximal position). The limit switch in housing 29communicates electrically with the control console 46 via cabling 41.Virtually any suitable equivalent position-sensing devices could beemployed in place of the limit switch. For example, the housing 29 couldbe sized and configured to accomodate an absolute position transducer soas to communicate absolute position to the control console 46. Theinformation provided by such an absolute position transducer could beemployed in conjunction with modified reconstruction algorithms forimage reconstruction, even during manual operation of the probe drivemodule 20.

Upon the probe drive module 20 reaching its most proximal position, thepointer 24c associated with the positioning arm 24 registers with themarking "10" on the scale 60 of housing 22. Of course, the ultrasonicimaging scan need not necessarily be conducted over the entire range of0-10 marked on the scale 60 and thus could be terminated at any time bythe physician simply releasing the foot-switch 27 or by simply pivotingthe probe drive module 20 into its manually-operable condition.

Those skilled in this art will recognize that a number of equivalentmechanical and/or electrical means could be employed. For example,locking slides, latches and quarter-turn screws could be used to allowengagement and disengagement of the probe drive module with the lineartranslation module. A flexible drive shaft connects the lineartranslation module to a rate-controlled motor which controls theautomatic linear translation rate. The motor is most preferably locatedin a separate fixed base unit, but could be provided as in an integralpart of the linear translation module, if desired.

Furthermore, various translation rates associated with the motor may beselected for various purposes. For example, slow rates give ample timefor the physician to examine the real-time images in cases where time isnot a limiting factor. The rate upper limit is governed by the proberotation rate and the effective thickness of the imaging data slicesgenerated by the probe, such that there is no (or an acceptable) gapbetween successive imaging data slices. This would prevent missingdiscernible features during vascular imaging with automatic translation.The effective thickness is governed by the ultrasonic beamcharacteristics of the probe. For some applications, the translation maybe discontinuous (i.e., gated to an electrocardiogram) for use withmodified algorithms or programmed to translate a fixed distancediscontinuously.

Thus, while the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. An automated longitudinal position translator for an ultrasonic imaging probe having a distally located ultrasound transducer subassembly comprising:a probe drive module adapted to being operatively coupled to the imaging probe so as to allow for longitudinal shifting of the ultrasound transducer subassembly of the probe between spaced-apart positions; and a motor-driven linear translation module connectable to said probe drive module to effect motor-driven longitudinal translation of said probe drive module to thereby responsively longitudinally shift said ultrasound transducer subassembly; and mounting structures for mounting said probe drive module to said translation module to allow for relative pivotal movements between an automatically-operable condition wherein said probe drive module is capable of being coupled to said motor-driven translation module to effect said motor-driven longitudinal translation thereof, and a manually-operable condition wherein said probe drive module is capable of being longitudinally shifted manually; a pair of elongate guide rails; forward and rearward transverse support arms connected to and spanning the distance between said pair of elongate guide rails; wherein said probe drive module is slidably coupled to said pair of guide rails so as to be capable of reciprocal longitudinal displacements therealong between said forward and rearward transverse support arms; and wherein said probe drive module is pivotally movable between said automatically-operable condition and a manually-operable condition by pivotal movement of said forward and rearward transverse support arms about said one guide rail.
 2. A position translator as in claim 1 wherein said linear translation module includes a pair of restraining posts adapted to contact respective ones of said forward and rearward transverse support arms in interference fit so as to releasably restrain said probe drive module in said automatically-operable condition.
 3. A method of obtaining a three-dimensioned image of a vessel, said method comprising the steps of:providing a probe drive module which is fixedly connected to the ultrasound imaging probe and operably connected to a stationary linear translation module and slidably connected to a guide rail; rotating the ultrasound imaging probe with the probe drive module while longitudinally shifting the ultrasound imaging probe with the linear translation module; and maintaining a constant rate of longitudinal movement of the linear translation module, thereby maintaining a substantially constant rate of longitudinal movement of the ultrasound imaging probe; and continuously pulsing and receiving echoes with the ultrasound transducer while rotating and longitudinally scanning the ultrasound probe through the transducer.
 4. An automated longitudinal position translator for an ultrasonic imaging probe having a distally located ultrasound transducer subassembly comprising:a prove drive module adapted to being operatively coupled to the imaging probe so as to allow for longitudinal shifting of the ultrasound transducer subassembly of the probe between spaced-apart positions; a motor-driven linear translation module connectable to said probe drive module to effect motor-driven longitudinal translation of said probe drive module to thereby responsively longitudinally shift said ultrasound transducer subassembly; wherein said ultrasound transducer subassembly of said ultrasonic imaging probe includes a flexible rotatable drive element disposed within a flexible guide catheter sheath, and wherein said probe drive unit includes: a longitudinally fixed but rotatable drive coupling capable of being fixedly attached to the proximal end of said rotatable drive member; and a longitudinally adjustable coupling which is longitudinally adjustable with respect to said rotatable drive coupling and which is capable of being fixedly attached to the proximal end of said guide catheter sheath, wherein said longitudinally adjustable coupling includes: a clamshell-hinged, barrel-shaped housing having a longitudinally extending slot; and a radially extending positioning arm coupled to said housing for longitudinal sliding movement within said slot and having a cavity formed therein for securely engaging the proximal end of said guide member or other members affixed to said guide member.
 5. A position translator as in claim 4 wherein said proximal end of said probe assembly includes a coupling member associated with said guide sheath, said positioning arm defines a cradle surface which is sized and configured to support said coupling member such that said coupling member and said positioning arm are movable as a unit between retracted and advanced positions.
 6. A position translator as in claim 5 wherein said housing includes upper and lower housing sections coupled to one another for relative pivotal movements between open and closed conditions.
 7. A position translator as in claim 6, wherein said lower housing section defines an inner bearing surface for supporting said positioning arm during movements thereof between said advanced and retracted positions, and wherein said upper bearing surface defines a surface for capturing said coupling member within said housing when said upper and lower housing sections are in said closed condition but permitting movement of said coupling member as a unit with said positioning arm.
 8. A position translator as in claim 7, wherein said housing defines a longitudinally extending slot to accommodate movement of said positioning arm between said advanced and retracted positions.
 9. A position translator as in claim 8, wherein said slot is defined by opposing edge regions associated with said upper and lower housing sections.
 10. A position translator as in claim 7, wherein said positioning arm is pivotally coupled to said housing such that said positioning arm, said upper housing section, and said lower housing section are capable of independent relative pivotal movement about a common pivot axis.
 11. A position translator as in claim 4, wherein said housing includes a scale in operative association with said positioning arm, and wherein said positioning arm includes an indicator adjacent to said scale.
 12. An ultrasonic imaging system capable of radial and longitudinal scanning of a vessel of the body comprising:a guide sheath capable of insertion within the body; an imaging probe comprising a transducer mounted at the distal end of a flexible drive shaft, said imaging probe slidably housed within the guide sheath; a rotational drive module capable of rotating the imaging probe within the guide sheath; a linear translation module capable of linearly translating the imaging probe within the guide sheath by translating the rotational drive module while maintaining the guide sheath in a fixed longitudinal position; said linear translation module being operably connected to the rotational drive module by means of a screw gear driven by the linear translation module; a first long guide rail fixed relative to the linear translation module and guide sheath, said guide rail being slidably coupled to the rotational drive module and serving to stabilize the rotational drive module while the rotational drive module is translated.
 13. The ultrasonic imaging system of claim 12 further comprising a clutch means for operably connecting and disconnecting the rotational drive module from the linear translational module.
 14. The ultrasonic imaging system of claim 12 further comprising a second long guide rail parallel to the first long guide rail and also slidably coupled to the rotational drive module thereby providing additional stability of the rotational drive module during translation thereof.
 15. An automated longitudinal position translator for ultrasonic imaging probes having a flexible drive shaft and distally located transducer comprising:a rotational drive motor and a rotational drive unit, said rotational drive unit operatively connecting said rotational device motor to the proximal end of the flexible drive shaft; a linear translation motor and a linear translation module, said linear translation module operatively connecting said linear drive motor to the rotational drive unit and being capable of linearly translating the rotational drive unit in a longitudinal direction relative to the axis of the imaging probe and at a continuous constant rate of linear translation, thereby imparting longitudinal linear translation to the ultrasonic imaging probe; at least one guide rail, upon which the rotational drive unit is slidably mounted, said guide rail serving to maintain the translation of the rotational drive unit in the longitudinal direction; an imaging probe guide sheath with its proximal end fixed in space relative to linear translation module, so that linear translation of the rotational drive unit and imaging probe will result in linear translation of the imaging probe within the guide sheath; an ultrasound transceiver operatively connected to the ultrasound transducer, said transceiver capable of sending and receiving signals to the ultrasound transducer while the transducer is simultaneously rotated by the rotational drive unit and translated by the linear translation module; and a signal processor capable of processing signals received from the transducer into three-dimensional visual representations on a video screen, said signal processor capable of processing all transducer signals received while the transducer is rotated and translated at constant rates.
 16. A method of three-dimensional ultrasound imaging of a lumen comprising the steps of:providing an ultrasound imaging probe comprised of a transducer mounted on a drive shaft; providing a rotational drive motor and a rotational drive unit operatively connecting said rotational drive motor to the drive shaft; providing a linear translation motor and a linear translation module, said linear translation module operatively connecting said linear translation motor to the imaging probe; providing an ultrasound transceiver operatively connected to the transducer to activate the transducer at a constant pulse rate and receive signals from the transducer; simultaneously rotating the imaging probe continuously and linearly translating the imaging probe continuously while activating the transducer and receiving signals from the transducer; and processing the signals received from the transducer during simultaneous rotation and linear translation to construct a three-dimensional image of the lumen.
 17. The method of claim 16 comprising the additional steps of:slidably mounting the rotational device unit on a fixed guide rail; and providing a guide sheath around the imaging probe and fixing the longitudinal position of the guide sheath relative to the linear translation module so that the imaging probe translates within the guide sheath.
 18. An automated longitudinal position translator for ultrasonic imaging probes having a distally located ultrasound transducer subassembly comprising:a probe drive module adapted to being operatively coupled to the imaging probe so as to allow for longitudinal shifting of the ultrasound transducer subassembly of the probe between spaced-apart positions; and a motor-driven linear translation module connectable to said probe drive module to effect motor-driven longitudinal translation of said probe drive module to thereby responsively longitudinally shift said ultrasound transducer subassembly; and wherein said linear translation module includes a motor-driven screw, and wherein said probe drive module is threadably connectable to said motor-driven screw such that rotation of said screw in a selected direction causes said probe drive module to be longitudinally shifted relative to said linear translation module; and mounting structures for mounting said probe drive module to said translation module to allow said probe drive module to be moved between an automatically-operable condition wherein said probe drive module is threadably engaged with said motor-driven screw, and a manually-operable condition wherein said probe drive module is disengaged from said motor-driven screw.
 19. An intravascular probe assembly comprising:a guide sheath having proximal and distal extremities; a probe element disposed within said guide sheath for longitudinal movements towards and away from said distal extremity thereof; and a motor-driven linear translator adapted to being coupled operatively to said probe element and said guide sheath to effect motor-assisted longitudinal shifting of said probe element relative to said distal extremity of said guide sheath; and a probe positioning module to longitudinally position said probe element relative to said distal extremity of said guide sheath, said linear translator being coupled operatively to said probe positioning module to provide motor-driven longitudinal positioning of said probe element; and said linear translator including a motor-driven screw which is threadably engaged with said probe positioning module such that rotation of said motor-driven screw responsively longitudinally moves said probe positioning module which thereby in turn longitudinally shifts said probe element; and mounting structures for mounting said probe positioning module to said linear translator to allow said probe positioning module to be moved between two operable conditions, one of said operable conditions being whereby the probe positioning module is disengaged from said motor-driven screw to allow for manual longitudinal shifting of said probe element thereby.
 20. An automated longitudinal position translator for ultrasonic imaging probes having a distally located ultrasound transducer subassembly comprising:a probe drive module adapted to being operatively coupled to the imaging probe so as to allow for longitudinal shifting of the ultrasound transducer subassembly of the probe between spaced-apart positions; and a motor-driven linear translation module connectable to said probe drive module to effect motor-driven longitudinal translation of said probe drive module to thereby responsively longitudinally shift said ultrasound transducer subassembly; and mounting structures for mounting said probe drive module to said translation module to allow for relative pivotal movements between an automatically-operable condition wherein said probe drive module is capable of being coupled to said motor-driven translation module to effect said motor-driven longitudinal translation thereof, and a manually-operable condition wherein said probe drive module is capable of being longitudinally shifted manually.
 21. A position translator as in claim 20, wherein said mounting structures include an elongate guide rail, and wherein said probe drive module is slidably and/or pivotally coupled to said guide rail. 